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FIBRE EXTRACTION

The processes of fibre extraction are varied, and depend on the effectiveness of the wet processing such as bleaching and dyeing of coir and also varied end uses.
Traditional fibre extraction
The traditional production of fibres from the husks is a laborious and time-consuming process. After separating of the nut, the husks are processed by various retting techniques generally in ponds of brackish waters (for three to six months) or in backwaters or lagoons. This requires 10-12 months of anaerobic (bacterial) fermentation

By retting, the husk are softened and can be decorticated and the fibre is extracted by beating, which is usually done by hand. After hackling, washing and drying (in the shade) the fibre is loosened manually and cleaned. The remaining residual pith - which was previously considered a waste problem - has recently found new profitable markets as a peat moss substitute for horticultural production.

Traditional practices of this kind yield the highest quality of (white) fibre for spinning and weaving. Retted fibre from green husks is the most suitable fibre for dyeing and bleaching.

For the production of more coarse brown yarns shorter periods of retting may be applied. These find an increasing outlet in geotextile applications.

Mechanical Extraction

Alternatively, mechanical processes using either defibering or decorticating equipment process the husks after only five days of immersion in water tanks. Crushing the husk in a breaker opens the fibres. By using revolving "drums" the coarse long fibre is separated from the short woody parts and the pith. The stronger fibres are washed, cleaned, dried, hackled and combed.

Green decortication and microbial treatments

New environment friendly methods for fibre production are of interest. These can be locally exploited on relative small-scale, and have the potential to produce a more constant quality of fibres. Novel developments by the Central Coir Research Institute, under Coir Board, using a biotechnological approach with specific microbial enzymes have reduced the retting time substantially to three to five days. High quality fibre production has been maintained.

Similar protocols can be developed to enhance the properties of the fibres in regard to surface properties such as smoothness and porosity. By using specific (microbial) lignolytic enzymes (laccase/phenoloxidase), the fibre surface can be bleached (or activated to react more easily with the dyes).

QUALITY OF FIBRE

Retted Coir Fibre / White Fibre

Retted coir fibre, also called white fibre, is extracted from green natural coconut husks after retting in flowing, circulating or changed water for a period of minimum three months. However, if the fibre is made out of precrushed husks the retting period could be reduced suitably. The fibre shall be free from moisture and impurities.

Grade	Colour	Maximum impurities percent by weight
1	Natural bright	2.0
2	Natural light brown and / or light grey	3.0
3	Natural brown and / or grey	5.0
4	Natural dark brown and / or dark grey	7.0

Length of Fibre

The length of fibres shall be designated as follows:

Designation	Length cm.
'Long'	Over 15
'Medium'	Over 10 and upto 15
'Short'	Over 5 and upto 10
'Bit'	Upto and including 5

Brown Fibre

Brown fibre is mechanically extracted from the dry husks of matured and ripe coconut after soaking these husks in water. The fibre shall be free from moisture and impurities

Length of fibre

The mechanically extracted coir fibre shall be grouped based on the length.

Group	Length (mm)
Long fibres	Above 200
Medium fibers	Above 150 and upto 200
Short fibres	Above 50 and upto 150

Percent by mass of 'Long', 'Medium' and 'Short' fibres and impurities in bristle coir fibre

Grade	Long Fibres Min.	Medium fibres Max.	Short Fibres Max.	Impurities Max.
Bristle fibre
Grade I	50	30	20	4
Grade II	40	25	35	5

Percent by mass of 'Long', 'Medium' and 'Short' fibres and impurities in Mattress coir Fibre

	Long/Medium Fibres Min.	Short Fibres	Impurities
Mattress fibre	10	90	20

Percent by mass of 'Long', 'Medium' and 'Short' fibres and impurities in Decorticated Coir Fibre

Grade	Long Fibres Min.	Medium fibres Max.	Short Fibres Max.	Impurities Max.
Grade I	20	30	50	7
Grade II	20	25	55	12

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